Three new luminescent Cd(II)-MOFs by regulating the tetracarboxylate and auxiliary co-ligands, displaying high sensitivity for Fe(3+) in aqueous solution.

Abstract

Three new Cd(ii)-MOFs, [Cd(L1)0.5(bpp)] (), [Cd(L1)0.5(bipy)] (), and [Cd(L2)0.5(bipy)] () [H4Ln = (1,1':4',1''-terphenyl)-2',x,x'',5'-tetracarboxylic acid (n = 1, x = 3, and n = 2, x = 4), bpp = 1,3-di(4-pyridyl)propane, and bipy = 2,2'-bipyridine], have been synthesized using Cd(ii) ions and isomeric H4Ln ligands in the presence of auxiliary ligands via solvothermal reaction, and have been fully characterized by elemental analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Complex is a three-dimensional (3D) pillar-layered network built from L1(4-) and bridging bpp co-ligands with a binodal (4,8)-connected gsp2 topology and a symbol of (4(4)·6(2))(4(16)·6(12)). was successfully synthesized using bipy instead of the bpp ligand used to assemble giving a 2D 4-connected sql net. is a 3D reticular framework with [Cd2(COO)4] SBUs based on L2(4-) ligands, displaying a (4,4)-connected lvt (4(2)·8(4)) topology. X-ray diffraction analysis revealed that the structures of the MOFs can be mediated by the steric effect of the tetracarboxylate and secondary co-ligands. The solid-state luminescence properties of the MOFs were measured carefully by ultraviolet irradiation at room temperature. In particular, exhibited a high sensitivity for Fe(3+) in aqueous solutions of mixed metal ions, which makes it a promising crystalline material to be a luminescent probe for Fe(3+). Importantly, can keep its original framework and be reused in sensing experiments. The sensing mechanism has also been studied in detail.